In the related art, as set forth in, for example, Patent Document 1, there is a hybrid drive apparatus for a vehicle which includes an engine that generates power by fuel combustion, a motor generator that functions as an electric motor and a generator, a planetary gear mechanism that is capable of combining and then outputting driving forces input from the engine and the motor generator, and a transmission mechanism that is capable of outputting a rotation caused by a driving force from the planetary gear mechanism to the drive wheels while changing the speed of the rotation. In the hybrid drive apparatus disclosed in Patent Document 1, an output shaft of the motor generator, an output shaft of the engine and an input shaft of the continuously variable transmission mechanism are coupled respectively to a sun gear, ring gear and carrier of the planetary gear mechanism 30. Further, the hybrid drive apparatus includes a first clutch that can switch engagement/disengagement between the output shaft of the engine and the ring gear and a second clutch C2 that can switch engagement/disengagement between the carrier and the ring gear.
In the hybrid drive apparatus disclosed in Patent Document 1, the second clutch is provided between the ring gear and carrier of the planetary gear mechanism whose relative velocity is comparatively large. As a result, the differential rotation (slipping velocity) of the friction material becomes small when the second clutch is in a disengaged state. Thus, friction loss in the second clutch can be reduced, thereby achieving a corresponding improvement in the transmission efficiency of the hybrid drive apparatus.
However, in the hybrid drive apparatus disclosed in Patent Document 1, a rotation occurs to the ring gear of the planetary gear mechanism when the first and second clutches are in engagement. Consequently, a differential rotation (slipping velocity) occurs to the friction material of the brake provided between the ring gear and a fixing member such as a casing. Still, as far as in the hybrid drive apparatus disclosed in Patent Document 1, the brake is provided for fixing the ring gear to the fixing member, the differential rotation (slipping velocity) occurring to the brake cannot be fundamentally eliminated, causing a loss due to the differential rotation to the brake. In particular, the differential rotation occurring when the first and second clutches are in engagement causes a loss. Therefore, by reconsidering the hybrid drive apparatus disclosed in Patent Document 1 provided with the brake for fixing the ring gear of the planetary gear mechanism to the fixing member such as the casing, a hybrid drive apparatus with reduced loss may be established to achieve improvement in the transmission efficiency of the hybrid drive apparatus.
Further, in the hybrid drive apparatus disclosed in Patent Document 1, at the time of starting by driving forces of the motor (motor generator), the vehicle starts using a range in which the rotation speed of the motor rises from zero. However, in general, the motor efficiency is better in a range different from the range in which the rotation speed rises from zero. Therefore, by improving the configuration of the hybrid drive apparatus disclosed in Patent Document 1, the efficiency in the driving mode using the driving forces of the motor can further increase.